“Underclassman” is more like a good episode of the TV-lite “Nash Bridges” than a fully arrived feature film.

But within that worn formula of cop-shop banter and implausible car chases, lanky Nick Cannon offers some mild entertainment for teenagers looking for a safe bet at the multiplex.

“Underclassman” rests on a ridiculous high concept, offering further proof that Hollywood screenwriters should endure apprenticeships with a real police force before earning the right to bear scripts. Chillingly efficient seniors from a rich Los Angeles high school are stealing cars and dealing drugs. These blazer-wearing punks are so good that detectives can’t crack them – although the geek from the school newspaper had them figured out just before his mysterious death.

Is there a baby-faced cop in the house, eager to redeem himself undercover after wrecking 30 cars and most of Venice Beach in an ill-considered car chase? Of course there is. Enter Nick Cannon, who effectively lent his angry-young-man persona to “Drumline” and has recently tried moving over to romantic comedy (“Love Don’t Cost a Thing,” in 2003).

Cannon is a brash detective wannabe under the wise tutelage of police captain Cheech Marin. (Wait, maybe this really is a “Nash Bridges” episode.) Their relationship is actually the best thing about the movie, with Marin underplaying a part for once and providing Cannon sane advice.

Cannon hasn’t quite mastered the transition from reformed thug to freewheeling beefcake. He still pouts to an inordinate degree, as if his agent forgot to tell him he’s making a lot more money as a movie star than as a dabbler in rap.

The script also suffers from a surfeit of lame black-white jokes, as Cannon shows up at the lily-laden private school. The geekiest white kid on the basketball team promptly asks the undercover detective to show him a little love. Cringe-

worthy moments continue when Cannon meets the Spanish teacher, a Latina hottie who dresses for the homies instead of the homeroom.

As relatively safe teenage fodder, though, “Underclassman” is not a bad choice at the multiplex. Cannon gets better as he goes, loosening up the glare and using some of his charm reserves on Roselyn Sanchez, the Spanish teacher. Between Cannon, Marin, Sanchez and Kelly Hu as a detective colleague, “The Underclassman” has an appealing rainbow cast.

Don’t expect many twists for the ending. Cannon and his characters must live on, to see if he’ll fulfill his potential as a rising star of cool.

And action comedies set on California’s coast always end up in the water – I’m sure I’ve seen that boat-chase climax before. Maybe it was up the shoreline in San Francisco, with Don Johnson at the wheel and Marin shouting, “Nash! Look out for that barge!”

Michael Booth was a health care & health policy writer at The Denver Post before departing in 2013. He started his journalism career as an assistant foreign editor at The Washington Post before moving with family to Denver and taking a brief stint with the Denver Business Journal. During a 25-year career at The Post, he covered city and state politics, droughts, entertainment and wrote Sunday takeouts, and was part of two Pulitzer Prize-winning teams for breaking news coverage.

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